Chapter 28 Protista The Origins of Eukaryotic Diversity

1. Chapter 28Protista The Origins of Eukaryotic Diversity Overview Protista; In the past, a single kingdom Note; some closely related to Plants to Fungi or to Animals (So kingdom Protista has been abandoned !!! and various lineages are recognized as kingdoms in their own right) But; protist , eukaryotes that are not plants, animals, or fungi

3. Protists Are Extremely Diverse • With high structural and functional diversity • Most, unicellular, but colonial andmulticellular • Complex cellular; a single cell carry out all basic functions of specialized cells in a multicellular organism

4. Nutrition most diverse of all eukaryotes • Some arePhotoautotrophs, containing chloroplasts. or Heterotrophs, absorbing organic molecules or Ingesting food particles or Mixotrophs, combining photosynthesis and heterotrophic nutrition • Based on their roles in biological communities three groups a- Photosynthetic algal protists b- Ingestive protozoans c- absorptive protists • Very diverse habitats • Life cycles vary greatly a- exclusively asexual b- sexual life cycles, meiosis and syngamy (The fusion of two gametes in fertilization)

5. Protistan Diversity 1. modified mitochondria In Diplomonads and parabasalids (found in anaerobic environments) a-No plastids b- No DNA in their mitochondria c- electron transport chain (ETC), and the enzymes needed for the citric acid cycle d- Diplomonads have two equal-sized nuclei and multiple flagella example; Giardia intestinalis; parasite that lives in the intestines of mammals and causes diarrhea dormant stage Giardia contaminated drinking water from feces containing the parasite

7. Parabasalids include trichomonads Example; Trichomonas vaginalis, inhabits the vagina of human females • T. vaginalis outcompete beneficial bacteria and infect the vaginal lining when the normal acidity of the vagina is disturbed • The male urethra may also be infected but without symptoms • The infection is sexually transmitted. • Genetic studies of T. vaginalis suggest that non pathogenic species transformed by horizontal gene transfer from other vaginal bacteria, the gene allows T. vaginalis to feed on epithelial cells

8. 2. Internal structure Euglenozoans have flagella with a unique internal structure • Euglenozoa (a clade) that includes a- predatory heterotrophs b- photosynthetic autotrophs c- pathogenic parasites Distinguished by a- Presence of a spiral or crystalline rod inside their flagella b- disc-shaped mitochondrial cristae (infoldings) • The best-studied groups of euglenozoans are the kinetoplastids and euglenids

9. The kinetoplastids * single large mitochondrion associated with a unique organelle, the kinetoplast, carrying extranuclear DNA * symbiotic and include pathogenic parasites example,Trypanosoma causes ** African sleeping sickness, a disease spread by the African tsetse fly ** Chagas’ disease (leads to congestive heart failure) transmitted by bloodsucking bugs • Trypanosomes evade immune detection by switching surface proteins from generation to generation, preventing the host from developing immunity • One-third of Trypanosoma’s genome codes for these surface proteins

11. Euglenids Characterized by a- an anterior pocket from which one or two flagella emerge b- unique glucose polymer, paramylon (storage molecule) c- Euglena are autotrophic but can become heterotrophic in the dark d- Light detector: swelling near the base of the long flagellum; detects light that is not blocked by the eyespot; as a result, Euglena moves toward light of appropriate intensity, an important adaptation that enhances photosynthesis e-Long flagellum f- Short flagellum g- Nucleus h- Plasma membrane i- Paramylon granule j- Chloroplast k- Contractile vacuole l- Eyespot: pigmented organelle that functions as a light shield, allowing light from only a certain direction to strike the light detector m- Pellicle: protein bands beneath the plasma membrane that provide strength and flexibility ( Note; Euglena, no cell wall Other euglenids can phagocytose prey

12. Long flagellum Eyespot: pigmented organelle that functions as a light shield, allowing light from only a certain direction to strike the light detector Short flagellum Nucleus Contractile vacuole Euglena (LM) 5 µm Plasma membrane Pellicle: protein bands beneath the plasma membrane that provide strength and flexibility (Euglena lacks a cell wall) Chloroplast Paramylon granule Light detector: swelling near the base of the long flagellum; detects light that is not blocked by the eyespot; as a result, Euglena moves toward light of appropriate intensity, an important adaptation that enhances photosynthesis

13. 3. Sacs beneath the plasma membrane Alveolates Alveolata (a clade) have alveoli, small membrane-bound cavities, under the plasma membrane • Alveoli function is not known, but they may help stabilize the cell surface or regulate water and ion content • Alveolata includes • flagellated protists (dinoflagellates) 2) parasites (apicomplexans) 3) ciliates.

14. Apicomplexans * parasites of animals * some cause serious human diseases * Sporozoites (tiny infectious cells) * The parasites spread through their host as sporozoites * The sporozoites have at their apex a complex of organelles specialized for penetrating host cells and tissues of the host * Nonphotosynthetic plastid (apicoplast; vital functions including the synthesis of fatty acids) * Intricate life cycles (sexual and asexual stages and often require two or more different host species for completion. Example; Plasmodium, the parasite that causes malaria, spends part of its life in mosquitoes and part in humans)

16. The two-host life cycle of Plasmodium, the apicomplexan that causes malaria

17. The Malaria, a human disease Caused by Plasmodium, (spends part of its life in mosquitoes (Anopheles) and part in humans) • Managed In the 1960s through a- insecticides against the Anopheles mosquitoes b- drugs that killed the parasites in humans • But; Resistant varieties of Anopheles, to insecticides made; Plasmodium come back ( 300 million people are infected in the tropics, and up to 2 million die each year)

18. Plasmodium can escape from the immunity system (is evasive) * It can change its surface protein * No successful vaccine developed * thereby changing its “face” to the human immune system * It spends most of its time inside human liver and blood cells * The expression of most of the Plasmodium’s genes at specific points in its life cycle identified (2003) potential new targets for vaccines • Chloroquine (an antimalarial drug) ** but malaria Plasmodium developed resistance ** Identification of the resistance gene ** block drug resistance in Plasmodium

19. Ciliates a- diverse group of protists b- use of cilia to move and feed c- cilia * cover the cell surface * clustered into rows or tufts * leg-like structures constructed from many cilia * cilia are associated with a submembrane * ciliary movements coordinated by submembrane system of microtubules

20. Ciliates Nuclei * Two types of nuclei; 1- Macronuclei, large macronucleus(general cell regulation) 2- Micronuclei, tiny micronucleus(reproduction) * Macronucleus has dozens of copies of the ciliate’s genome. ** The genes are not organized into chromosomes but are packaged into small units with duplicates of a few genes ** Genes control the everyday functions of the cell such as feeding, waste removal, and water balance Ciliate reproduction * generally, asexually by binary fission of the macronucleus (no mitotic division) Example:Paramecium caudatum

22. Paramecium conjugation Genetic variation results from the sexual shuffling of genes which occurs through conjugation, during which two individuals exchange haploid micronuclei. • In ciliates, reproduction and conjugation are separate processes. • In a real sense, ciliates have “sex without reproduction.”

24. 4. Stramenopiles have hairy and smooth flagella. • The clade Stramenopila includes both heterotrophic and photosynthetic protists (some group of algae). • The name of this group is derived from the presence of numerous fine, hairlike projections on the flagella. • The heterotrophic stramenopiles, the oomycetes, include water molds, white rusts, and downy mildews. Stramenopile flagella • Many oomycetes have multinucleate filaments that resemble fungal hyphae.

25. Diatoms * unicellular algae * highly diverse group of protists, with an estimated 100,000 species * They are abundant members of both freshwater and marine plankton * store food reserves as the glucose polymer laminarin or, in a few diatoms, as oil * glasslike walls composed of hydrated silica embedded in an organic matrix * Wall; divided into two parts that overlap (like a shoebox and lid) * walls allow live diatoms to withstand immense pressure * defense for them from the crushing jaws of predators * Massive accumulations of fossilized diatoms are major constituents of diatomaceous earth Reproduction • diatoms reproduce asexually by mitosis • each daughter cell receiving half of the cell wall and regenerating a new second half • Some species form cysts as resistant stages • Sexual stages are not common • Sexual, involves the formation of eggs and amoeboid or flagellated sperm

27. Brown algae, or phaeophytes, (Seaweeds) • The largest and most complex protists known • Multicellular • most species are marine • Common along temperate coasts in areas of cool water and adequate nutrients • Their brown or olive color; presence of carotenoids in their plastids • Seaweeds (largest marine algae), • Brown, Red, & green Habitat the intertidal and subtidal zones of coastal waters • (This environment is characterized by extreme physical conditions, including wave forces and exposure to sun and drying conditions at low tide) Anatomy • complex multicellular anatomy • some differentiated tissues and organs that resemble those in plants • thallus, or body, of the seaweed. • a root-like holdfast • a stem-like stipe, • Leaf-like photosynthetic blades

29. The term “seaweed” refers to brown algae as well as some species of green and red algae. • The giant seaweeds known as kelps live in deep water beyond the intertidal zone (Kelp forest) • The stipes of these algae may be as long as 60 m Intertidal zone Seaweeds • cope with rough water • twice-daily low tides (expose the algae to hot sun and risk of desiccation) Seaweeds as sources of food and commodities • Many seaweeds are eaten by coastal people, * Laminaria (“kombu” in Japan) in soup * Porphyra (Japanese “nori”) * sushi wraps • Gel-forming substances, extracted in commercial operations * Algin from brown algae * Agar and carrageen from red algae are used as thickeners in food, lubricants in oil drilling, or culture media in microbiology

30. 5.Cercozoans have threadlike pseudopodia • Cercozoa; a newly recognized clade • Contains the amoebas (“amoeba” = protists that move and feed by means of pseudopodia) • Pseudopodia, cellular extensions that bulge from the cell surface • Amoeba movement, * It extends a pseudopodium and anchors the tip * Cytoplasm then streams into the pseudopodium • Cercozoa; amoeba threadlike pseudopodia • Cercozoans include; * Foraminiferans and are closely related to Radiolarians, which also have threadlike pseudopodia

32. Foraminiferans, or forams * Named for their porous shells, or tests. * Forams have ** multi-chambered, porous shells, consisting of organic materials hardened with calcium carbonate ** Pseudopodia extend through the pores for swimming, shell formation, and feeding ** symbioses with algae ** live in marine and fresh water ** Most live in sand or attach to rocks or algae ** abundant in the plankton ** forams fossils (90% of the described forams) ** calcareous skeletons of forams are important components of marine sediments Note: Fossil forams are often used as chronological markers to correlate the ages of sedimentary rocks from different parts of the world.

33. 6.Amoebozoans have lobe-shaped pseudopodia • Many species of amoebas that have lobe-shaped pseudopodia belong to the clade Amoebozoans,a-gymnamoebas b- entamoebas c- slime molds

34. 7. Red algae and green algae *closest relatives of land plants *Red algae have no flagellated stages in their life cycle (other eukaryotic algae do) * More than 6,000 known species of red algae, * Reddish due to the accessory pigment phycoerythrin * Coloration varies among species * Coloration depends on the depth that they inhabit * Some species lack pigmentation * Not pigmented, parasites on other red algae.

36. Red algae are the most common seaweeds in the warm coastal waters of tropical oceans • Inhabit deeper waters than other photosynthetic eukaryotes • Phycobilins; (photosynthetic pigment) allows them to absorb blue and green wavelengths that penetrate down to deep water, more than 260 m (Bahamas cost) • Some red algae live in fresh water or on land. • Most red algae are multicellular, with some reaching a size large enough to be called “seaweeds.”

37. The thalli of many red algal species are filamentous • The base of the thallus is usually differentiated into a simple holdfast • The life cycles of red algae are especially diverse • In the absence of flagella, fertilization depends entirely on water currents to bring gametes together

38. Green algae * grass-green chloroplasts * Similar in ultrastructure and pigment composition to chloroplasts of plants • Green algae and land plants are closely related evidence from; ** Molecular systematics ** Cellular morphology provide considerable • Divided into two main groups, a- Chlorophytes; 7,000 species, most are identified b- Charophyceans. • Most live in fresh water, but many are marine inhabitants. • Some chlorophytes inhabit damp soil, while others are specialized to live on glaciers and snowfields

39. Snow-dwelling chlorophytes carry out photosynthesis despite; * subfreezing temperatures * intense visible and ultraviolet radiation * protected by radiation-blocking compounds in their cytoplasm and by the snow itself (shield) • Some chlorophytes live symbiotically with fungi to form lichens, a mutualistic collective. • Large size and complexity in chlorophytes has evolved by three different mechanisms: • Formation of colonies of individual cells (e.g., Volvox). • The repeated division of nuclei without cytoplasmic division to form multinucleate filaments (e.g., Caulerpa). • The formation of true multicellular forms by cell division and cell differentiation (e.g., Ulva).

41. Some multicellular marinechlorophytes are seaweeds, large and complex • Complex life cycles, with both sexual and asexual reproductive stages • Most sexual species have biflagellated gametes with cup-shaped chloroplasts • Alternation of generations evolved in the life cycles of some green algae • The other main group of green algae are most closely related to land plants